Lapping machine



4 Sheets-Sheet 1 Filed April 14, 1961 May 14, 1963 G. c. HUNT 3,089,292

LAPPING MACHINE Filed April 14, 1961 l 4 Sheets.sheet g INVENTOR Geol/EEC. HUNT Fag BY ATTO R N EY May 14, 1963 G. c. HUNT 3,089,292

LAPPING MACHINE Filed April 14, 1961 4 Sheets-Sheet 3 W 9/ ZGEOVEIVETUNT May 14, 1963 G. c. HUNT 3,089,292

LAPPING MACHINE Filed April 14, 1961 4 Sheets-Sheet 4 ATTORNEY UnitedStates Patent O 1 3,089,292 LAPPING MACHINE Grover C. Hunt, Carlisle,Pa., assigner to Norton Cornpany, Worcester, Mass., a corporation ofMassachusetts Filed Apr. 14, 1961, Ser. No. 103,014 14 Claims. (Cl.51-118) The invention relates -to a lapping machine and moreparticularly to a lapping machine incorporating a pair of opposedannular cast iron laps arranged to finish the opposing surfaces of thinfrangible elements supported and displaced by carriers driven byopposing driving elements.

Various arrangements for supporting and driving opposing laps to finishthe opposing faces of various types of Work pieces are generally wellknown. However, the difficulties encountered in finishing the opposingsurfaces of generally flat Work pieces tend to increase as the thicknessto which the work pieces are-finished is reduced to a few thousandths ofan inch. These difficulties are intensified when such work piecesconsist of relatively brittle material such as germanium or silicon orthe like.

The instant invention contemplates apparatus for lapping thin brittlework pieces to a finished thickness of the order of .003 or less. Thisapparatus is further characterized by a capability for producingopposing flat surfaces of good quality on such work pieces whilemaintaining the work piece thickness uniform throughout and by thecapability of producing such surfaces more rapidly and without the riskof destroying other work pieces if one work piece should break duringthe lapping operation.

An object of this invention is the provision of power driven apparatusfor lapping a plurality of thin frangible work pieces to closetolerances with respect to surface finish and parallelism of the opposedflat surfaces.

Another object is the provision of driving means for opposed laps andfor a plurality of Work piece carriers interposed therebetween arrangedto produce relative motion of the respective elements such that the riskof fracturng thin frangible work pieces during the lapping operation isminimized, and that the risk of damaging additional work pieces isminimized if one work piece fractures during the lapping operation.

Still another object of this invention is the provision of supportingmeans for a lower lap arranged to preclude distortion of the lower lapby the supporting means when the lap is mounted thereon, said supportingmeans being readily adjustable to position the lapping surface of thelower lap in the desired plane.

Yet another object is the provision of an upper lap comprising a unitaryannular element having a relatively deep transverse section to renderthe upper lap rigid and thereby highly resistant to distortion.

A final object is the provision of a plurality of concentricallydisposed power transmitting means interconnecting a power source and therespective coacting rotatable elements of a lapping apparatus.

Other objects and advantages of the instant invention will be apparentfrom the following description considered `in relation lto the showingin the accompanying drawings wherein:

FIG. 1 is a vertical section through the preferred ernbodiment of theinstant invention taken substantially on line 1-1 of FIG. 2;

FIG. 2 is a plan View, partially broken away, with the upper lap inplace;

FIG. 3 is a plan view, partially broken away, with the upper lapremoved;

FIG. 4 is a detailed view of a portion of the gear train substantiallyon line 4 4 of FIG. l;

FIG. 5 is a detailed View of a portion of the gear train Itakensubstantially on line 5-5 of FIG. 1;

ICC

FIG. 6 is a vertical section through the upper lap taken on line 6-6 ofFIG. 2;

FIG. 7 is a vertical section, partially broken away, through the upperand lower laps shown in operative relation to a carrier encircling awork piece and to the driving elements for the work carrier showing thedistribution of a slurry to the work piece;

FIG. 8 is a vertical section in a radial plane through a perspectiveshowing partially broken away showing work piece carriers supported uponthe lower lap and operatively engaged by the respective inner and outerdriving elements with the upper lap shown displaced vertically from itslapping position; and

FIG. 9 is a detailed plan view partially broken away showing a modifiedwork carrier in operative relation to portions of the respective innerand outer driving elements.

yReferring now to the drawings wherein like reference numerals refer tolike or corresponding parts, the apparatus comprising the instantinvention, as illustrated in FIG. 1, comprises a base assembly generallydesignated by the reference numeral 10 arranged to support a pluralityof relatively rotatable elements together comprising a lapping device, adrive means, and means for transferring power from the drive means tothe respective rotating elements. As shown in FIG. 1, the base assembly19 includes a flat base plate 12 to which a plurality of verticallyextending legs 13 may be secured by means of suitable attachment meanssuch as screws 14. The upper ends of the respective legs 13 may besecured adjacent to the periphery of an annular top member generallydesignated by the numeral 16 by means of suitable attachment means suchas machine bolts 15. The annular top member 16 may conveniently consistof a central cylindrical sleeve or hub 17, a cylindrical upstandingouter rim 18, and an annular web 19 extending outwardly from the sleeve17 and sloped downwardly to join the rim 1% adjacent its lower edge.

A drive motor M coupled to a suitable gear reduction assembly 21 mayconveniently be mounted upon 4the base plate 12 by any suitableattachment means `such as screws not shown. The output shaft 22projecting vertically from the gear reduction assembly 21 is fitted withpinion gears 24 and 25 fixedly secured thereto to be driven by the motorM.

The base assembly 'additionally includes a first shaft supportingbracket 32 including a lower leg 32 secured to the base plate 12 and anupper leg 32 generally parallel to` and spaced from the lower leg 32'; asecond shaft supporting bracket 34 dependent from the top member 16 andsecured thereto by at least one machine bolt 15', which includes spacedparallel substantially elongated lower and upper legs 34' and 34"; athird shaft supporting bracket 36 depending from the top member 16 andsecured thereto by at least one machine lbolt 15, which includes spacedparallel substantially elongated lower and `upper legs 36 and 36"; and agenerally cylindrical bearing support assembly generally designated bythe reference numeral 38 `dependent from the central sleeve 17 of thetop member 16 and including segments 3S', 38, and 38" all securedfixedly to the sleeve 17 by through bolts not shown in FIG. 1.

The lapping device includes yfour major components, an upper lapassembly generally designated by the reference numeral 411, an innerdriving element generally ydesignated by the reference numeral 60, alower lap assembly ygenerally designated by the reference numeral 80 andan outer `driving element generally designated by the reference numerall100.

The upper lap assembly 40' includes an upper lap 41 .consisting of anannular cast yiron ring provided with a flat planar uninterruptedlapping surface 42 and having an inwardly sloping upper surface 43 andan outwardly sloping upper surface 44. The upper lap 41 is positionedand driven by a driving plate 45 disposed ooncentrically of the lap andprovided with a plurality of enlanged radially projected segments 46shaped -to be closely but freely intertted with the annular inner sideWall of the lap 41. At least one pin 47 is mounted in the upper lap 41so that it extends radially inwardly ltherefrom `for engagement with oneedge of at least one of the relatively enlarged segments 46 of thedriving plate 45. The driving plate 45 is mounted upon the upper end ofa shaft `48 with the joint therebetween covermed by a cap 49 secured inplace by an attachment bolt 50. The driving plate rests upon a shoulder59 on the shaft 48, and rotation of the driving plate 45 relative to theshaft 4S is precluded by a key 51. A shoulder 54 on the shaft 48 engagesthe inner race of a thrust bear-ing assembly 53 and the lower end of theshaft 48 is supported by a. bearing assembly 55 located within thebearing support assembly 318. The lower end of the shaft 48 is providedwith an extension -6 of reduced diameter arrangement to support aplurality of gears to be described in detail hereinbelow.

While the single pin 47 visible in FIG. 1 satisfies the minimumrequirement for driving engagement between the driving plate and the lap41, the lap 41 may be provided with three pins 47 projecting radiallyinwardly from the lap -41 for engagement with one edge of each of thethree radially projected segments 46 of the driving plate 45, as shownin FIG. 2.

The inner driving element 60 includes a gear 61 provided with peripheralteeth 62 and secured by attachment means such as machine bolts 63 to`the upper end of a hollow spindle 68 provided with a shoulder 74engaging the inner race of -a thrust bearing assembly 73 and supportedadjacent its lower end by a bearing assembly 75 mounted Within thebearing support assembly 38.

The lower lap asesmbly 80 includes a lower lap 81 consisting of anannular cast iron ring provided with a rlat planar uninterrupted lappingsurface 82. The lower lap 81 is provided with three equally spacedgenerally cylindrical recesses 83 to receive the respective heads 84 ofthree adjustably positioned machine bolts -85 threadedly engaged withand projecting from the upper surface of a spider I86 adjacent therespective ends of three equally spaced radially extending legs y87thereof. A dependent hollow spindle 88, either Iiixedly secured to orformed integrally with the spider 86, as shown in FIG. 1, is supportedadjacent its upper end upon a thrust bearing assembly 9=3 with its innerrace in engagement with a shoulder 94 at the upper end of the spindle88, and adjacent its lower end by a bearing assembly 95 contained withinthe beaning support assembly 38.

The outer driving element 100 includes a ring gear 101 provided withinternal gear teeth 102 and secured by suitable attachment means such asbolts 103 to the upper rim 105 of a frame member generally designated bythe reference numeral 104 including a hub 106 and a plurality ofsupporting arms 107 each including a horizontal portion extendingradially from the hub 106 .and a vertical portion extending verticallyIfro-m the horizontal portion to the rim 105. The 'frame member 104,either iixedly secured tot or formed integrally with a hollow spindle108 depending therefrom, as shown in FIG. l, is rotatably supported by athrust bearing assembly 113 disposed with its inner race in engagementwith the shoulder 114 and vby the bearing assembly 115.

From consideration of the showing in FIG. 1, it will be evident that thebearing assemblies 113 and 115 supporting the spindle 108 and the framemember 104 and thence the ring gear 101 are in turn supported within thesleeve 17 of the top member 16; that the bearing assemblies 93 yand 95supporting the spindle 88 and the spider 86 and vthereby the lower lap81 yare supported by the spindle 108 and the support assembly 38,respectively; that the bearing assemblies 73 'and 75 supporting thespindle 68 and thereby the lgear 61 are supported by the -spindle 88 andthe support assembly 38, respectively; and that the bearing assemblies53I and 55 supporting the shaft 48 and thereby the driving plate 45 forthe upper lap 41 are supported by the spindle 68 and the supportassembly 38, respectively.

The gear train `for driving the upper lap assembly 40 and moreparticularly the upper lap 41 includes a spur gear 121 mounted rotatablyupon the shaft extension 56 and connected to the driving element of aconventional over-running clutch assembly 123 mounted upon the extension56 with its driven element keyed thereto as shown in FIG. l. With thisgearing arrangement, rotation of the output shaft 22 produces rotationof the pinion gear 24 transmitted to the spui gear 121 and thencethrough the driving and driven elements of the over-running clutchassembly 123 to the extension 56 to produce rotation of the shaft 48 andthe driving plate 45 keyed thereto so that the segment 46 engaging thepin 47 produces rotation fof the upper lap 41.

The gear train for driving the lower lap assembly and more particularlythe lower lap 81 includes a spur gear 131 rotatably mounted upon a shaft141 and connected to the driving element of another conventionalover-running clutch assembly 123 mounted upon the shaft 141 and havingits driven element keyed thereto as shown in FIG. 1. The shaft 141,rotatably supported in a pair of bearing assemblies 143 and 145respectively mounted in the legs 34 and 34" of the brackets 34, has aspur gear 133 xedly secured to its upper end for engagement with a spurgear 13'5 fxedly secured to the lower end of the spindle 68. With thisgearing arrangement, rotation of the pinion gear 24 produced by rotationof the output shaft 22 is transferred to the spur gear 131 and thencethrough the driving and driven elements of the over-running clutchassembly 123 to the shaft 141 for transmission to the spur gear 133 torotate the spur gear 13S and Ithe spindle 68v to rotate the lower lap 81resting upon the heads 84 of the bolts 85 projectingfrom the legs 87 ofthe spider 86. An additional showing of the relationship between thepinion gear 24 and the spur gear 131 respectively supported on theoutput shaft 22 and the shaft 141 is provided in FIG. 5.

The gear train for driving the inner driving element 60 and moreparticularly the gear 61 includes the pinion gear 25 described above asfixedly secured to the output shaft 22 of the reduction gear assembly21, coaxially disposed spur gears 151 and 152 inter-connected forrotation as a unit and both rotatably supported upon the extension 56 ofthe shaft 48. A spur gear 153 -Xedly Secured to and rotatable with asupporting shaft 161 rotatably supported in bearing assemblies 163 and165 mounted in the respective legs 32' and 32" of the bracket 32, apinion gear 154 also iixedly secured to and rotatable with the shaft161, and a spur gear 155 lixedly secured to the lower end of the spindle68, arranged as shown in FIG. 1 so that rotation of the pinion 25produces r0- tation of the spindle 68 transmitted to the gear 61 throughthe attachment bolts 63 securing gear 61 to the spindle 68. Therelationship between the pinion gear 25 secured to output sha-ft 22 andspur gear 151 rotatable on shaft extension 56 is also illustrated inFIG. 5 along with a further showing of the relationship between the spurgear 153 iixedly secured to shaft 161 and spur gear 152 iixedly securedto spur gear 151 and rotatable therewith upon the shaft extension 56.

The gear train for driving the outer driving element and moreparticularly the ring gear 101 includes all of the elements for drivingthe inner driving element assembly 60 enumerated above from the pinion25 through the pinion 154, and additionally includes a spur gear 171 anda spur gear 172 secured to the opposite ends of a shaft 181 rotatablysupported in a pair of bearing epesses assemblies A183 and 185respectively supported in the legs 36 and 36" of the bracket 36, and aspur gear 173 fixedly secured to the lower end of spindle 108, so thatrotary motion of the pinion '25 transmitted to the pinion 154 is alsotransmitted through spur gears 171 and y172 to spur gear 173 and thencethrough the spindle 108 to the frame member 104 to which the ring gear101 is secured by attachment bolts 103 for rotation therewith. A furthershowing of the relationship between spur gear 171 fixedly secured toshaft 181, the pinion gear '154 xedly secured to shaft 161, and spurgear 155 tixedly secured to spindle 68 is provided in FIG. 4.

From consideration of the above descriptions of the respective geartrains, it will be evident that the rate of rotation of each of the fourrelatively rotatable elements of the lapping device of the instantinvention relative to the other three relatively rotatable elements ofthis device is determined by the design of the particular gear traincontrolling the rotation of that element, notwithstanding the fact thatall of these elements are rotated concurrently in response to rotarymotion of a single driving means illustrated in FIG. 1 as an electricmotor M.

A plurality of work pieces to be lapped may he Supported in a series ofcarriers 201 shown best in FIG. 3 each provided with peripheral gearteeth 202 for engagement with the external teeth 62 of the driving gear61 and with the internal teeth 102 of the external driving ring gear`101 so -that rotation of the gear 61 and the ring gear 101 in oppositedirections produces ro-tation of the respective work carriers 201 abouttheir respective centers. In addition, the gear trains for therespective driving elements 60 and 100 are so arranged that therespective carriers are advanced slowly along a path concentric to theaxis of rotation of the central shaft 48 and the respective spindlesconcentric thereto. In addition, the respective laps 41 and 81 aredriven in opposite directions at substantially the same speed with asmall difference of the order of one tooth in the gear trains for therespective laps in order to preclude a cyclic relationship between therotation of the upper lap and the rotation of the lower lap. Theoperative relationship between the respective relatively rotatableelements of the lapping device and the work piece carriers as well asthe relative movement of these elements and the carriers is bestillustrated in FIG. 8.

It is to be understood that the internal configuration of the carriers201 may be varied as necessary to accommodate different sizes and shapesof work pieces W. For example, the carriers 2011 may be provided with asingle relatively large concentric opening 203` as shown best in FIGS. 3and 8 to accommodate an individual relatively large circular work piece.Alternatively, the carriers 201 may be provided with one or moreeccentric openings 203 therethrough, one configuration of such carriersbeing illustrated in FIG. 9. It will be evident that, when the carrieris sufhciently larger than the work piece openings required, there maybe two or more such openings through a single carrier, eccentric of andpreferably equally spaced about the center of the carrier.

Another advantage inherent in the design of the lapping devicecharacterizing the instant invention is its capability for finishing aplurality of relatively small work pieces W contained within a singlerelatively much larger opening through a carrier 201 as illustrated inlFlG. 9.

In preparation for the operation of the device comprising the instantinvention, the upper lap 41 must be removed from its normal operatingposition as shown in FIGS. l and 2. Since the ring comprising the upperlap 41 is relatively heavy, its removal may be facilitated by providinga pair of hand holds therefor in the form of transverse openings 191therethrough shown best in FIGS. 2 and 6.

With the upper lap 41 removed, a series of work piece carriers 201 maybe inserted between the gear 61 and the ring gear 101 to rest upon thelapping surface 82 of the lower lap 81 at regularly spaced intervals inthe manner best illustrated in the secontional view comprising FIG. 3.In this connection, while FIG. 3 is taken through line 3 3 of FIG. 1 forthe clearest showing of the relationship between the respective carriers201 and the driving gear 61, it is to be understood that the carrierscan be inserted into this machine without removing the driving plate 45from the upper end of the shaft 48. After the Work piece carriers 201have been positioned as shown in FIG. 3, the work pieces W may be placedwithin the respective carriers `for the lapping operation.

When the upper lap 41 is replaced, its correct alignment with the shaft40 is -assured by the interaction of the inner edge of the lap 41 withthe peripheral surfaces of the respective segments 46 projectingradially from the driving plate 45 and the lap 41 is positioned forrotation by the `driving plate 45 when each pin 47 projecting radiallyinwardly from the lap 41 is disposed against the edge of a segment 46which will move toward that pin 47 when the motor M is energized.

When the upper lap 41 has been positioned in its proper relationship tothe respective work pieces as shown best in FIG. 7, the drive motor Mmay lbe energized to produce rotation of the output shaft 22 and therebyrotate the several rotatable elements of the lapping device includingthe upper lap assembly 40, the inner driving element 60, the lower lapassembly 80, and the outer driving element 100. The relative rotation ofthese elements as determined by the respective gear trains therefor iscontinued until the lapping operation is completed.

Throughout the lapping operation, an abrasive slurry consisting oflabrasive particles and a suitable liquid vehicle therefor may besupplied to the work pieces being lapped by applying the abrasive slurryeither manually as with :a brush or automatically by means of a slurrydistribution system to the upper sloping surfaces 43 and 44 of the upperlap 41. The manner in which the abrasive 'slurry is delivered to thework pieces during the lapping operation is best illustrated in FIG. 7illustrating a fiow of the abrasive slurry down the upper lslopingsurfaces 43 and 44 and thence down the vertical inner and outer sidewalls of the lap 41 for delivery to the upper surfaces -of therespective carriers 201 for delivery to the space between the erspectivelapping surfaces 42 and 82 as the work piece carriers 201 are rotatedtherebetween.

The embodiment of the instant invention described above and illustratedin the accompanying drawings is intended to be considered exemplary onlyrather than 'including driving means provided with an annular portion4rotatably supported upon said first driving element for independentrotation about the same predetermined axis and -a lower lap meanssupported and driven thereby, a second driving element including anannular portion rotatably supported by the first lap assembly forindependent rotation about the same predetermined axis, a second lapassembly including driving means provided with a portion rotatablysupported by said second driving element for independent rotation aboutthe same predetermined axis and an upper lap means driven therebypositioned above and supported by the lower lap means, power`transmission means for transmitting rotary motion from said motor meansto said upper lap means, power transmission means for transmittingrotary motion from said motor means to said lower lap means, powertransmission means for transmitting rotary motion from said motor meansto the second driving element, power transmission means for transmittingrotary motion from said motor means to the rst driving element, and aplurality of circular work piece carrier means interposed between saidupper and said lower lap means in operative engagement with said Irstand second driving elements for rotation of the respective circularcarrier means concurrently about their respective axes and about thesame predetermined axis.

2. Apparatus as described in claim l, wherein said lirst lap assemblyfurther includes three symmetrically spaced supporting elementsprojecting upwardly from and individually adjustable vertically relativeto the driving means thereof, and three symmetrically spaced recessedportions in the underside of said lower lap means so disposed as toreceive the three symmetrically spaced supporting elements in supportingand driving engagement therewith.

3. Lapping apparatus comprising a base, motor means mounted upon saidbase arranged to produce rotary motion, -an outer driving elementincluding `an annular outer driving means and supporting means thereforhaving -an elongated annular portion rotatably supported upon said basefor rotation about a predetermined vertical axis, a lap driving meansincluding spaced vertically projecting portions arranged to support anddrive an annular lap mounted thereon and an elongated annular portionrotatably supported upon said outer driving element for rotation `aboutthe predetermined axis, a lower llap means disposed concentrically ofand within said outer driving element supported upon and driven by thelap driving means supported by said outer driving element, an innerdriving element including a circular driving means disposedconcentrically within and substantially co-planar with said annularouter driving means and supporting means therefor including an elongatedannular portion rotatably supported by the lap driving means supportingsaid lower lap means for rotation about the predetermined axis, a lapdriving means including radially projecting portions for positioning andfor driving engagement with an upper lap and an elongated portionsupported by the inner driving element lfor rotation about thepredetermined axis, an upper lap means in engagement with the drivingmeans therefor positioned above the lower lap means and concentric ofthe predetermined axis, power transmission means for transmittingrot-ary motion from said motor means to said upper lap means via the`driving means therefor, power transmission means for transmittingrotary motion from the motor means to said ilower lap means via thedrive means therefor, power transmission means for transmitting rotarymotion from the motor means to the inner driving means via the innerdriving element, power transmission means for transmitting rotary motionfrom the motor means to the outer driving means via the outer ldrivingelement, a plurality of circular Work piece carrier means interposedbetween said upper and said lower laps in operative engagement with saidinne-r and outer driving means for rotation of the respective circularcarrier means concurrently about their respective axes and about thepredetermined axis.

4. Apparatus as described in claimV 3, wherein said lower lap means isprovided with three symmetrically spaced recessed portions in theunder-surface thereof, and the spaced projecting portions of the lapdriving means for said lower lap means consist of three symmetricallyspaced supporting elements individually vertically adjustable -andpositioned for intertitting engagement with the respective recessedportions of said lower lap means for supporting and driving engagementtherewith, whereby said lower lap means may be precisely positioned withits lapping surface in a plane perpendicular to the predetermined axiswithout distortion of said lower lap means.

5. Lapping apparatus comprising a base, variable speed motor meansmounted upon said base arranged to produce rotary motion, an outerdriving element including an annular outer carrier dri-ving means andsupporting means therefor including an annular portion dependingtherefrom rotatably supported upon said base for rotation about apredetermined vertical axis, a lap driving means for a lower lap meansincluding spaced vertically projecting portions arranged to support anddrive an annular lap mounted thereon and an elongated portion dependenttherefrom rotatably supported upon said outer driving element -forindependent rotation about the same predetermined axis, an annular lowerlap means disposed concentrically of and within said outer drivingelement supported upon and driven by the lap driving means supported bysaid outer driving element, an inner driving element including acircular carrier driving means disposed concentrically within andsubstantially co-planar with said annular outer driving means and anelongated annular portion dependent therefrom rotatably supported uponthe driving means supporting said lower lap means for independentrotation about the same predetermined axis, a lap driving means for anupper lap means including radially projecting portions for positioningand for driving engagement with an upper lap means and an elongatedportion dependent therefrom rotatably supported upon the inner drivingelement for independent rotation about the same predetermined axis, anannular upper lap means in engagement with the driving means thereforpositioned above and supported by the lower lap means and concentric ofthe same predetermined axis, power transmission means for transmittingrotary motion from said motor means to said upper lap means via thedependent portion of the driving means therefor, power transmissionmeans for transmitting rotary motion from and said motor means to saidlower lap means via the dependent portion of the driving means therefor,power transmission means for transmitting rotary motion from said motormeans to the inner carrier driving means via the dependent portion ofthe inner driving element, power transmission means for transmittingrotary motion from said motor means to the outer carrier driving meansvia the dependent portion of the outer driving element, la plurality ofcircular work piece carrier means interposed between said upper and saidlower lap means in operative engagement with said inner and outercarrier driving means for rotation of the respective circular carriermeans concurrently about their respective axes and about the samepredetermined axis.

6. Lapping apparatus comprising a base, motor means mounted upon saidbase arranged to produce rotary motion, :an outer driving elementincluding an annular driving member and supporting means thereforincluding an annular portion rotatably supported upon said base forrotation about a predetermined vertical axis, a lap driving meansincluding spaced projecting portions arranged to support and drive a lapmounted thereon and an elongated annular portion rotatably supportedwithin the elongated portion of said outer driving element forindependent rotation about the same predetermined axis, a lower lapdisposed concentrically of and within 4said outer driving elementsupported upon and driven by the 1ap driving means supported by saidouter driving element, an inner driving element including a circulardriving member disposed concentrically within and substantiallyco-planar with said annular driving member and an elongated annularportion rotatably supported within the elongated portion of the drivingmeans supporting said lower lap for indenpendent rotation about the samepredetermined axis, a driving means `for an upper lap includingprojecting port-ions for positioning and for driving engagement with anupper lap and an elongated portion rotatably supported within theelongated portion of the inner driving element for independent rotationabout the same predetermined axis, an upper lap in engagement with thedriving means therefor positioned about the -lower lap and concentric ofthe same predetermined axis, power transmission means -for transmittingrotary motion from said motor means to said upper lap via the drivingmeans therefor, power transmission means for transmitting rotary motionfrom the motor means to said lower lap via the driving means therefor,power transmission means for -transmitting rotary motion from the motormeans to the inner driving member via the inner driving element, power-transmission means for transmitting rotary motion from the motor meansto the outer driving member via the outer driving element, a pluralityof circular work piece carrier means interposed between said upper andsaid lower -laps in operative engagement with said inner and outerdriving elements for rotation of the respective circular carrier meansconcurrently about their respective axes and 4about the samepredetermined axis, the relationship between the power transmissionmeans for said upper lap and the power transmission means for said lowerlap being such that the upper and lower laps are rotated simultaneouslyin opposite directions about the predetermined axis at substantially thesame but not idenic-al relaively -high rates, and the differentialrelationship between the -power transmission means for said outerdriving member and said inner driving member being such that the carriermeans are rotated :about their respective axes and about thepredetermined axis at relatively very low rates as compared to the ratesof rotation of the respective laps.

7. Lapping apparatus comprising `an upper lap supported for rotationabout -a predetermined vertical axis,

first lap driving means disposed in operative engagement With ysaidupper lap and including an elongated dependent portion thereof disposedand supported for rotation about 'the predetermined axis, a firstdriving element disposed adjacent said upper lap, ya first supportingmeans connected to said first driving element including an elongated`annular dependent portion thereof disposed :and supported for rotationabout the predetermined axis, means supporting said first driving meansrotatably upon said first supporting means, a lower lap mounted belowsaid upper lap for rotation 'about the predetermined axis, a second lapdriving means supporting and driving said lower lap by engagementtherewith yand including an elongated annular dependent portion thereofdisposed and supported for rotation about the predetermined axis, meanssupporting said first supporting means rotatably upon said seconddriving means, a second driving element disposed adjacent said upper lapand spaced from said first driving element, a second supporting meansconnected to said second driving element including an elongated annulardependent portion thereof disposed and -supported for rotation about thepredeterm-ined axis, means supporting said sec-ond driving meansrotatably upon said second supporting means, a base, means supportingsaid second supporting means rotatably upon said base, a plurality of`generally planar work piece carrier means interposed between said upperlap and said lower lap and positioned in operative engagement with saidfirst and second driving elements, motor means mounted upon said baseand connecting means supported upon said base operatively connectingsaid motor means to said upper lap through said first driving means, tosaid first driving element through said first supporting means, to saidlower lap through said second driving means, and to said second drivingelement through said second supporting means, whereby rotation of saidmotor means produces rotation of said upper lap, lsaid lower lap, saidfirst driving element, and -said second driving element in predetermineddirections :at predetermined relative rates.

8. Lapping apparatus comprising an annular upper lap supported forrotation about a fixed predetermined vertical axis, first lap drivingmeans disposed in operative engagement with said upper lap and includingan elon- 10 gated portion dependent therefrom disposed and sup-v portedfor rotation about the predetermined axis, a first driving elementdisposed concentr-ically of said upper lap, a first supporting meansconnected to said first driving element including an elongated annularportion dependent therefrom disposed and supported for rotation aboutthe predetermined axis, an annular flower lap mounted beneath 'andadjacent said upper lap for rotation about the predetermined axis, Iasecond =lap driving means support ing and driving said lower lap byengagement therewith and including `an elongated annular portiondependent therefrom disposed and supported for rotation about thepredetermined axis, a second driving element disposed concentrical'lyyof said upper lap, a second supporting means connected to `said seconddriving element including an elongated annular portion dependenttherefrom dis posed and supported for rotation about the predeterminedtaxis, -a base, first bearing means supporting said first driving meansupon said first supporting means, second bearing means supporting saidfirst supporting means upon said second driving means, third bearingmeans supporting -said second driving means upon said second supportingmeans, fourth bearing means supporting said second supporting means uponsaid base, a plurality of generally planar work piece carrier meansinterposed between said upper lap and said lower lap and positioned inoperative engagement with said first and second driving elements, motormeans mounted upon said base and power transmission means supported uponsaid base operatively connecting said motor means to `said upper lapthrough said first driving means, to said first driving element throughsaid first supporting means, to said lower lap through said seconddriving means, and to said second driving element through said secondsupporting means, whereby rotation of said motor means produces rotationof said upper lap, said lower lap, said first driving element, and saidsecond driving element in predetermined directions at predeterminedrelative rates.

9. Lapping apparatus comprising a base, an upper lap supported forrotation about a fixed predetermined axis, iirst llap driving meansdisposed in operative engagement with said upper lap and including anelongated portion disposed and supported for rotation about thepredetermined axis, a first driving element disposed adjacent said upperlap land a coact-ing lower lap, a first supporting means connected tosaid first driving element including an elongated annular portiondisposed and supported for rotation about the predetermined axis, alower lap mounted adjacent said upper lap for rotation `about thepredetermined axis, a second lap driving means supporting and drivingsaid lower lap by engagement therewith and including an elongatedannular portion disposed and supported for rotation about thepredetermined axis, a second driving element disposed adjacent saidupper and lower laps and spaced from said first driving element, asecond supporting means connected to said second driving elementincluding an alongated annular portion disposed and supported forrotation about the predetermined axis, first spaced bearing meanssupporting said first driving means upon said first supporting means,second spaced bearing means supporting said first supporting means uponsaid second driving means, third spaced bearing means supporting saidsecond driving means upon said second supporting means, fourth spacedbearing means supporting said second supporting means upon said base, aplurality of generally circular work piece carrier means interposedbetween said upper lap and said lower lap and positioned in operativeengagement with said first and second driving elements, motor meansmounted upon said base, power transmission means supported upon saidbase operatively connecting said mot-or means to said upper lap throughsaid first driving means and to said lower lap through said seconddriving means so as to rotate said upper and lower laps in oppositedirections at substantially the same but not identical rates, and powerItransmission means supported upon said base operatively connecting saidmotor means to said first driving element through said first supportingmeans, and to said -second driving element through said secondsupporting means so `as to rotate said first and second driving elementsin opposite directions at different rates relatively much slower thanthe yrates of rotation of said laps,

10. Lapping apparatus comprising a relatively fixed base, first andsecond lap assemblies, first and second work carrier driving elements,each lap assembly and each driving element including one of fourgenerally cylindrical depending portions all rotatably supported uponsaid base for independent rotation about a common vertical axis, and asingle drive means operatively connected separately to each of saiddepending portions so as to produce rotation of each of said lapassemblies and each of said driving elements in a predetermineddirection at a predetermined rate, so that a plurality of circular Workpiece carrier means interposed between said .t

first and said second lap assemblies and in operative engagement withsaid first and said second driving elements are rotated concurrentlyabout their respective axes and about the common vertical axis.

11. Lapping apparatus comprising a relatively fixed base, upper andlower opposed annular lap assemblies, inner and outer spaced opposedgenerally coplanar work carrier driving elements, each lap assembly andeach driving element including one of four generally cylindricalconcentrically disposed depending portions all rotatably supported uponsaid base for independent rotation about a common vertical axis, adrivemeans fixedly mounted relative to said base, and first, second,third `and fourth power transmission means all operatively coupled tosaid drive means and each connected to one of said four dependingportions to produce rotation of the upper and lower lap assemblies inopposite directions at similar but not identical rates and rotation of.the inner and outer driving elements in opposite directions atrespective rates such that circular work carriers engaged therebetweenare advanced slowly about the common vertical axis as they are rotatedabout their respective central axes.

12. Lapping apparatus as described in claim l1, Wherein said upper lapassembly includes an annular lap member provided on its underside withan uninterrupted annular horizontal lapping surface intersected at atleast one ed-ge thereof by a vertical surface extending upwardlytherefrom, and having at least one truncated conical upper surfaceintersecting the upper edge of each vertical surface, so that anabrasive slurry deposited at one or more points on each truncated.conical upper surface of said annular lap member is distributed overeach truncated conical upper surface and the intersecting verticalsurface and thence into the space between the respective lap assemblies.

13. Lapping apparatus as described in claim 11, wherein said upper lapassembly includes an annular lap member provided on its underside withan uninterrupted annular horizontal lapping surface intersected at eachedge thereof `by a vertical surface extending upwardly therefrom, andhaving an upper surface including truncated `conical portionsintersecting the upper edge of each vertical surface, so that anabrasive slurry deposited at one or more points on each truncatedconical portion of the upper surface of said annular lap member isdistributed over eachtruncated conical portion of the upper surface andthe intersecting vertical surface and thence into the space between therespective lap assemblies.

14. In lapping apparatus including a relatively fixed base, and drivemeans mounted xedly relative to said base, a lower lap assemblyincluding a lap driving means mounted upon the ibase for rotation abouta fixed predetermined vertical axis and operatively connected to thedriveV means, three symmetrically spaced lap supporting elementsprojecting upwardly from and individually `adjustable verticallyrelative to said lap driving means, and

a lower lap means having a planar lapping surface and provided withthree symmetrically spaced recessed portions in the underside thereof sodisposed as to receive said three symmetrically spaced lap supportingelements in supporting and driving engagement therewith, where-References Cited inthe file of this patent UNTTED STATES PATENTS c1,541,001 Searles June 9, 1925 1,579,876 Lutz Apr. 9, 1926 2,709,321Indge May 31, 1955 2,973,605 Carman et al. Mar. 7, 1961

10. LAPPING APPARATUS COMPRISING A RELATIVELY FIXED BASE, FIRST ANDSECOND LAP ASSEMBLIES, FIRST AND SECOND WORK CARRIER DRIVING ELEMENTS,EACH LAP ASSEMBLY AND EACH DRIVING ELEMENT INCLUDING ONE OF FOURGENERALLY CYLINDRICAL DEPENDING PORTIONS ALL ROTATABLY SUPPORTED UPONSAID BASE FOR INDEPENDENT ROTATION ABOUT A COMMON VERTICAL AXIS, AND ASINGLE DRIVE MEANS OPERATIVELY CONNECTED SEPARATELY TO EACH OF SAIDDEPENDING PORTIONS SO AS TO PRODUCE ROTATION OF EACH OF SAID LAPASSEMBLIES AND EACH OF SAID DRIVING ELEMENTS IN A PREDETERMINEDDIRECTION AT A PREDETERMINED RATE, SO THAT A PLURALITY OF CIRCULAR WORKPIECE CARRIER MEANS INTERPOSED BETWEEN SAID FIRST AND SAID SECOND LAPASSEMBLIES AND IN OPERATIVE ENGAGEMENT WITH SAID FIRST AND SAID SECONDDRIVING ELEMENTS ARE ROTATED CONCURRENTLY ABOUT THEIR RESPECTIVE AXESAND ABOUT THE COMMON VERTICAL AXIS.